Ocassional dropouts

I’ve been having this issue ever since I bought an audio interface (Behringer U-Phoria UMC204HD, recording at 96kHz, 24bit). Didn’t have this issue previously when I would record directly from the line input on the PCs integrated soundcard (Realtek ALC261, recording at 48kHz, 16bit).
I’m having occasional dropouts (once every 4-10 minutes or so). While that might not be such a big problem, it is for me, considering I’m archiving my LP collection. Also, in the past I used to get notified by Audacity when dropouts would occur, and label the specific zones where I had dropouts, but that doesn’t seem to happen anymore. The option under “Recording” is enabled, for detecting dropouts.
Is there something I could do to mitigate this issue, or perhaps troubleshoot?
I’m not running anything in the background, except the browser. That sometimes also causes the dropouts, but it still happens if I close it, albeit not as frequent. Restarting seems to fix the issue temporarily, but after a while it happens again.
I’m using Debian, and I installed Audacity through apt. Audacity version 2.2.2

$ uname -a
Linux SecondPC 4.19.0-11-amd64 #1 SMP Debian 4.19.146-1 (2020-09-17) x86_64 GNU/Linux
$ apt policy audacity
  Installed:   2.2.2-1+b1
  Candidate: 2.2.2-1+b1
  Version table:
 *** 2.2.2-1+b1 500
        500 http://ftp.dk.debian.org/debian buster/main amd64 Packages
        100 /var/lib/dpkg/status

(Behringer U-Phoria UMC204HD, recording at 96kHz, 24bit). Didn’t have this issue previously when I would record directly from the line input on the PCs integrated soundcard (Realtek ALC261, recording at 48kHz, 16bit).

You might try 48kHz with the new interface. It’s less data so you are less likely to get buffer overflow and a dropout/glitch. And 48kHz is still better than human hearing. …And WAY better than analog vinyl. :wink:

And/or you can try increasing the [u]Latency/Buffer length[/u].

Or, if you’re not getting excess noise with your regular soundcard, the other important specs (frequency response & distortion) are usually better than human hearing so it may be perfectly adequate… Noise is usually the only issue with the line input. (Microphone inputs are a different story…)

I’m not an expert on fixing dropouts (and I’m a Windows guy) but it’s usually caused by “something else” interrupting the system and hogging the system for a few milliseconds too long, and the recording buffer overflows. Your operating system is always multitasking even if you’re only running one application.


You could try using JACK to manage your audio interface. And does Debian have a low-latency kernel?

The benefit of using JACK is that audio can be processed with real-time priority and a low-latency kernel can assist in responsiveness to audio data.

I use JACKD2 with my Focusrite Scarlett 2i2 under a low-latency 5.4.0 kernel on my i5-5400U laptop. You get the odd XRUN but nothing like you describe. And 48kHz is plenty for the sampling rate.

ATB, Neil

I’m likely not going to decrease the sample rate, or bit depth. It’s the reason I got the interface in to begin with, if I were to record from the soundcard, what’s the point in the interface? Plus I’m not 100% sure how noisy the soundcard is.
I did try to increase the buffer length, got up to 1000 ms, but the occasional dropout still occurs, and I’m guessing that if I were to increase this to even more, it won’t help much. I have a feeling it’s not something related to latency.
As I said earlier, even when using this interface, previously I used to get notified when I would get dropouts. This has all changed ever since I moved my PC further away from my turntable setup. Since the USB cable from the interface is a tad too short, I had to use an USB cable extension. Could this be culprit?
If so, what could I use as an alternative?

I’ll look into this. And yes, there’s the Liquorix kernel which is meant for multimedia and gaming.

I’m guessing this would also allow me to prioritise recording, even when browsing in the background?

Keep it at 24-bit. That should lower the noise floor and allow you more headroom.

For normal audio, sample rates above 48 kHz don’t really give any benefit. Whereas bit depth controls the digital noise floor level, the sample rate controls the upper cut-off frequency. “Perfect” human hearing goes up close to 20 kHz, beyond which we are all totally deaf (for most people the upper frequency limit is much lower). 48 kHz sample rate supports frequencies way beyond what we can hear - close to 24 kHz. Most audio interfaces are limited by their analog electronics to around 20 kHz, so the only benefit to recording higher than 48 kHz is advertising hype. (There are marginal benefits for 96 kHz in some studio setups that use a word clock to synchronise multiple pieces of hardware). Frequencies above 20 kHz are present in vinyl recordings, but fortunately we can’t hear them because they are mostly just noise.

That’s significant. It indicates that the dropouts are occurring “upstream” from Audacity. The bottle neck is not between Audacity and disk storage, but between analog input and Audacity. Recording at 48 kHz may be sufficient to fix the problem - I’d try that first.

Also, use the “hw” device in the Device Toolbar that corresponds to the Behringer. That will bypass PulseAudio and give you a more direct connection between Audacity and the DAC.